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351.
Michael G. B. Drew Debashree Das Senjuti De Jnan Prakash Naskar Dipankar Datta 《Journal of chemical crystallography》2008,38(7):507-512
Abstract The X-ray crystal structure of the 1:2 condensate (1) of hydrazine hydrate and 4-methyl-imidazole-5-carboxaldehyde has been
determined. The molecule is centrosymmetric crystallising in the space group Fddd with cell dimensions: a = 10.557(14), b = 17.062(22), c = 24.759(27) ?. Fourier map shows that the NH hydrogen atom of each imidazole moiety has equal possibility of occupying any
of its two ring N atoms. This poses the possibility of finding three tautomers in 1 in the solid state. Consideration of the H-bonding pattern observed in 1 and related B3LYP/6-311+G(2d,p) calculations show that only two tautomers are present in the solid state. The situation is
compared with that in the structure of 4(5)-nitro-5(4)-methoxy-imidazole reported previously by Kubicki.
Graphical Abstract
The inherent disorder of the ring N–H hydrogen atoms in the shown centrosymmetric molecule (blue, C; deep blue, N; grey, H)
which contains two imidazole moieties, poses the possibility of the coexistence of three tautomers in the solid state. The
observed and theoretical [from B3LYP/6-311+G(2d,p) calculations] H-bonding pattern indicate that only two tautomers are present
in the solid state.
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352.
Dibya Prakash Biswal Dipankar Singha Dr. Jagannath Panda Dr. Malay Kumar Rana 《Chemphyschem》2023,24(21):e202300311
UiO-66-NH2-IM, a fluorescent metal-organic framework (MOF), was synthesized by post-synthetic modification of UiO-66-NH2 with 2-imidazole carboxaldehyde via a Schiff base reaction. It was examined using various characterization techniques (PXRD, FTIR, NMR, SEM, TGA, UV-Vis DRS, and photoluminescence spectroscopy). The emissive feature of UiO-66-NH2-IM was utilized to detect volatile organic compounds (VOCs), metal ions, and anions, such as acetone, Fe3+, and carbonate (CO32−). Acetone turns off the high luminescence of UiO-66-NH2-IM in DMSO, with the limit of detection (LOD) being 3.6 ppm. Similarly, Fe3+ in an aqueous medium is detected at LOD=0.67 μM (0.04 ppm) via quenching. On the contrary, CO32− in an aqueous medium significantly enhances the luminescence of UiO-66-NH2-IM, which is detected with extremely high sensitivity (LOD=1.16 μM, i. e., 0.07 ppm). Large Stern-Volmer constant, Ksv, and low LOD values indicate excellent sensitivity of the post-synthetic MOF. Experimental data supported by density functional theory (DFT) calculations discern photo-induced electron transfer (PET), resonance energy transfer (RET), inner filter effect (IFE), or proton abstraction as putative sensing mechanisms. NMR and computational studies propose a proton abstraction mechanism for luminescence enhancement with CO32−. Moreover, the optical behavior of the post-synthetic material toward analytes is recyclable. 相似文献